Scope of the Problem: Hip fractures occur in 280,000 Americans, over 5,000 per week. During the next 40 years, the number of hip fractures is likely to exceed 500,000 annually, and the estimated annual health care costs will reach a staggering $9.8 billion. Hip fracture patients are at risk of a 30% mortality rate and impairment of independence and quality of life. Treatment Options: Hip fractures are commonly treated with hip replacement, or arthroplasty. Two common types of arthroplasty exist - total hip arthroplasty (THA) and hemi-arthroplasty (HA). Advocates of hemi-arthroplasty (HA) focus upon reduced dislocation rates, lower rates of deep vein thrombosis, shorter operating times, less blood loss, and a technically less demanding procedure. Surgeons supporting THA perceive benefits in improving patient function and improving quality of life. Methodological limitations of previous studies, as well as their small sample sizes and resulting wide confidence intervals, have left the optimal operative approach unresolved. Objectives: Pilot Study: To assess the feasibility (recruitment, compliance, and follow-up) of conducting a large randomized trial comparing patients over age 50 years with a displaced femoral neck fracture treated with either THA or HA. Definitive Study: In patients over 50 years who have sustained a displaced femoral neck fracture, what is the rate of reoperation at 2 years when THA versus HA is used as the surgical treatment? We will also evaluate patient function and quality of life. Study Design: We propose a PILOT study to evaluate the feasibility of a multicenter, concealed randomized trial design, comparing total hip arthroplasty (THA) versus hemi-arthroplasty (HA) in patients with displaced femoral neck fractures. This pilot study will recruit 100 patients, across 10 US sites: (1) Boston Medical Center, Boston, MA, (2) Lahey Medical Center, Burlington, MA, (3) Greenville Hospital Systems, Greenville, SC, (4) University of Cincinnati, Cincinnati, OH, (5) East Texas Medical Center, Tyler, TX, (6) Thomas Jefferson Hospital, Philadelphia, PA, (7) Miami Valley Hospital, Dayton, OH, (8) Mayo Clinic, Rochester, MN, (9) St. Elizabeth Health Center, Youngstown, OH, and (10) Duke University Medical Center, Durham, NC. Patients will be randomized to either THA or HA and treated by surgeons with expertise in that technique. We will independently adjudicate revision surgery rates and collect functional outcome data at hospital discharge, 2 weeks, 10 weeks, 3, 6, 9, and 12 months for the pilot study. Hypothesis: For this pilot, we hypothesize that our recruitment estimates, patient follow-up, study compliance, and data quality will be sufficiently high to support feasibility of a large pivotal RCT. For the large trial, we hypothesize that total hip arthroplasty will have similar or lower rates of re-operation (primary outcome) and higher functional outcome scores (secondary outcome) at 24 months compared with hemi-arthroplasty. Potential Impact: This trial will not only change current orthopaedic practice, but will set a benchmark for the conduct of future orthopaedic trials.